It was a good way to see which cities both at home, and abroad, were becoming tech hubs, with their own ecosystems and startup communities to rival Silicon Valley.

But the next question is: just how successful are these accelerators and incubators? Do they actually churn out companies that become notable and disruptive?

Well, there is an easy way to find out: to look at their graduates, how much they have raised and/or how much they are worth. We picked a few of the top accelerators in the country to take a deeper dive.

Techstars, for example, has graduated a total of 292 companies, of which 223 have received a total of $571.8 million. 230 of its graduates are currently active. Another 30 have failed and the other 32 were acquired.

Its companies average over $1.6 million in outside venture capital raised after leaving. The average valuation for Techstars alumni is $4.3 million, or a total of $1.5 billion, the accelerator revealed to me,

Located in Boston, Boulder, Chicago, New York City, Seattle, London, and Austin, Techstars puts $118,000 in each company, through $18,000 in seed funding and an optional $100,000 convertible debt note.

TechStars founder David Cohen will be a keynote speaker at our Splash London event on June 19. We're taking applications now to get the top 10 pan-European and London-based startups in front of him and top VCs. Apply here.

Some of TechStars notable graduates include Sendgrid, which raised $27.3 million; Socialthing, which was acquired by AOL in 2008; DailyBurn, which was acquired by Mindspark Interactive Network in 2010; Cloudability: raised $9.8 million; Contently which raised $12 million; DigitalOcean, which raised $40.2 million, valued at $153 million; and Localytics, which raised $24.8 million

Meanwhile, 500 Startups has graduated over 250 companies from nine cohorts. Of those, none have IPOed, 10 of them have been acquired, and 50, or 20% of them have failed.

The Mountain View-based accelerator gives $50,000 for 5% equity. The accelerator also participates in follow-on investments up to $200,000 for startups that are doing well.

The total value of those 250 graduates is $1.25 billion, for an average valuation of $5 million per company, Dave McClure, founding partner of 500 Startups, told me. That is about a 5 times increase from when the accelerator invests. The total raised for its graduates is roughly $200 million.

Some of notable companies that have gone through include Intercom, which has raised over $30 million; Visually, which has raised over $12 million; Applauze, which raised over $10 million; MindSnacks, which raised $8 million; and Punchd, which was acquired by Google.

Then there is the big dog: Y Combinator, which has, since 2005, funded over 630 startups for a combined valuation of over $20 billion, and a total of $2.09 billion raised, for an average of $3.7 million, I was told.

The company has some very totable graduates, including Dropbox, which has raised $607 million, valued at $10 billion; Airbnb, which has raised $326 million, valued at $2.7 billion; Stripe, which has raised $120 million, valued at $1.83 billion; Optimizely, which has raised $31.2 million; Pebble, which has raised $25.7 million; and Disqus, which has raised $10.5 million

Those six companies alone above have raised $1.1 billion.

The Mountain View-based accelerator gives startups a seed investment of up to $20,000 in exchange for a 2-10% stake in the company.

What does failure mean?

Now let's take all of those numbers together and add them up.

The three accelerators have funded 1,172 companies, which have a combined valuation of $22.75 billion, and total raised of $2.78 billion.

Only 80 of the companies that came out of TechStars and 500 Startups have "failed." Now, for the sake of comparison, it should be noted that what TechStars considers to be a failure is not the same as 500 Startups.

For TechStars, a "failure" is a company that has ceased operations. If it still operating, but has not raised any money, then it has not failed according to that standard.

500 Startups, on the other hand, doesn't just count companies that no longer exist, but also those with a return on investment that is valued at less than 1X. That includes companies with below 1X value acquisitions, "zombie" companies, which are still alive but with little chance of a greater than 1X exit.

Obviously any accelerator program is going to have both failures and successes, but, as you can see, each of these programs have already churned out some very successful companies, with a huge success rate.

Taking a look at the numbers, its hard to see these programs as anything but a success.

(Editor's note: On May 6-7, we'll take a look at accelerators (new and old) at our upcoming Splash Oakland event to learn what's working and what's not and some of the new strategies appearing. We'll have the founders and managing directors of StartX, Alchemist Accelerator, Berkely Skydeck, and SfunCube. Check out the event here.)